It is a well known condition that many recreational swimming areas are underutilized because such waters are often occupied by various forms of sea animals which are perceived as jeopardizing the safety of would-be swimmers.
Prior means including sonic signals, electrical charges and chemical deterrants have been employed to discourage marine animals from occupying human swimming areas. Another common means to exclude marine animals from bathing areas involves various forms of physical barriers, particularly fences and nets, which encircle such swimming areas. Prior marine nets and fences are typically supported by either (1) a series of permanently positioned rigid vertical fence poles, or (2) as series of floats connected to the top of the nets floating at the surface of the water.
A problem of prior devices which use permanent rigid fence poles is that such nets cannot be easily relocated. It is also a problem that installation of permanent poles is a difficult and costly operation. Also, since the location of the fence is, by its nature, fixed in the water, it is often difficult to make repairs to such devices. Another problem of fixed position fences is that they generally must be oversized so as to allow for wide ranges of water levels, particularly in waters subject to current and tide variations. Another problem of fixed rigid poles is that in order to remain erect they must be constructed and installed with sufficient structural strength to overcome extremes of forces exerted thereupon by wind, tide, waves and debris.
Prior devices which comprise nets supported by floats on the surface of the water either sink under their own weight so that the top of the net is below the surface, or lift up from the bottom of the water so that the bottom of the net is above the floor of waterway, when the depth of the water increases as occurs with an incoming tide. Similarly, with an outgoing tide, such prior devices develop superfulous slack in the net in which swimmers may become entangled. Another problem of such prior devices is that all of the net is at all times underwater, and it is therefore not visible to swimmers--thereby providing an unobservable underwater hazard to swimmers.
It is also a problem of such prior devices that a continuous, or nearly continuous, float system, or "boom", is usually required in order to support the net. A problem which is inherent in floating booms is that tidal drag exerted on them is often very high and results in large forces exerted upon anchoring devices at the end of such booms.